Polytrichum Formosum Research Articles

Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

This study explores basic physiological features and time relations of recovery of photosynthetic activity and CO2 uptake following rehydration of a desiccation-tolerant moss in relation to the full temporal sequence of cytological changes associated with recovery to the normal hydrated state. It seeks reconciliation of the apparently conflicting published physiological and cytological evidence on recovery from desiccation in bryophytes. Observations were made of water-stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and of structural and ultrastructural changes by light and transmission electron microscopy. Net CO2 uptake fell to zero at approx. 40 % RWC, paralleling the fluorescence parameter PhiPSII at 200 micromol m(-2) s(-1) PPFD. On re-wetting the moss after 9-18 d desiccation, the initially negative net CO2 uptake became positive 10-30 min after re-wetting, restoring a net carbon balance after approx. 0.3-1 h. The parameter Fv/Fm reached approx. 80 % of its pre-desiccation value within approx. 10 min of re-wetting. In the presence of the protein-synthesis inhibitors chloramphenicol and cycloheximide, recovery of Fv/Fm (and CO2 exchange) proceeded normally in the dark, but declined rapidly in the light. Though initial recovery was rapid, both net CO2 uptake and Fv/Fm required approx. 24 h to recover completely to pre-desiccation values. The fixation protocols produced neither swelling of tissues nor plasmolysis. Thylakoids, grana and mitochondrial cristae remained intact throughout the drying-re-wetting cycle, but there were striking changes in the form of the organelles, especially the chloroplasts, which had prominent lobes and lamellar extensions in the normally hydrated state, but rounded off when desiccated, returning slowly to their normal state within approx. 24 h of re-wetting. Sub-cellular events during desiccation and re-wetting were generally similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

This study explores basic physiological features and time relations of recovery of photosynthetic activity and CO2 uptake following rehydration of a desiccation-tolerant moss in relation to the full temporal sequence of cytological changes associated with recovery to the normal hydrated state. It seeks reconciliation of the apparently conflicting published physiological and cytological evidence on recovery from desiccation in bryophytes. Observations were made of water-stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and of structural and ultrastructural changes by light and transmission electron microscopy. Net CO2 uptake fell to zero at approx. 40 % RWC, paralleling the fluorescence parameter PhiPSII at 200 micromol m(-2) s(-1) PPFD. On re-wetting the moss after 9-18 d desiccation, the initially negative net CO2 uptake became positive 10-30 min after re-wetting, restoring a net carbon balance after approx. 0.3-1 h. The parameter Fv/Fm reached approx. 80 % of its pre-desiccation value within approx. 10 min of re-wetting. In the presence of the protein-synthesis inhibitors chloramphenicol and cycloheximide, recovery of Fv/Fm (and CO2 exchange) proceeded normally in the dark, but declined rapidly in the light. Though initial recovery was rapid, both net CO2 uptake and Fv/Fm required approx. 24 h to recover completely to pre-desiccation values. The fixation protocols produced neither swelling of tissues nor plasmolysis. Thylakoids, grana and mitochondrial cristae remained intact throughout the drying-re-wetting cycle, but there were striking changes in the form of the organelles, especially the chloroplasts, which had prominent lobes and lamellar extensions in the normally hydrated state, but rounded off when desiccated, returning slowly to their normal state within approx. 24 h of re-wetting. Sub-cellular events during desiccation and re-wetting were generally similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery.

This study explores basic physiological features and time relations of recovery of photosynthetic activity and CO(2) uptake following rehydration of a desiccation-tolerant moss in relation to the full temporal sequence of cytological changes associated with recovery to the normal hydrated state. It seeks reconciliation of the apparently conflicting published physiological and cytological evidence on recovery from desiccation in bryophytes. Observations were made of water-stress responses and recovery using infrared gas analysis and modulated chlorophyll fluorescence, and of structural and ultrastructural changes by light and transmission electron microscopy. Net CO(2) uptake fell to zero at approx. 40 % RWC, paralleling the fluorescence parameter PhiPSII at 200 micromol m(-2) s(-1) PPFD. On re-wetting the moss after 9-18 d desiccation, the initially negative net CO(2) uptake became positive 10-30 min after re-wetting, restoring a net carbon balance after approx. 0.3-1 h. The parameter F(v)/F(m) reached approx. 80 % of its pre-desiccation value within approx. 10 min of re-wetting. In the presence of the protein-synthesis inhibitors chloramphenicol and cycloheximide, recovery of F(v)/F(m) (and CO(2) exchange) proceeded normally in the dark, but declined rapidly in the light. Though initial recovery was rapid, both net CO(2) uptake and F(v)/F(m) required approx. 24 h to recover completely to pre-desiccation values. The fixation protocols produced neither swelling of tissues nor plasmolysis. Thylakoids, grana and mitochondrial cristae remained intact throughout the drying-re-wetting cycle, but there were striking changes in the form of the organelles, especially the chloroplasts, which had prominent lobes and lamellar extensions in the normally hydrated state, but rounded off when desiccated, returning slowly to their normal state within approx. 24 h of re-wetting. Sub-cellular events during desiccation and re-wetting were generally similar to those seen in published data from the pteridophyte Selaginella lepidophylla. Initial recovery of respiration and photosynthesis (as of protein synthesis) is very rapid, and independent of protein synthesis, suggesting physical reactivation of systems conserved intact through desiccation and rehydration, but full recovery takes approx. 24 h. This is consistent with the cytological evidence, which shows the thylakoids and cristae remaining intact through the whole course of dehydration and rehydration. Substantial and co-ordinated changes in other cell components, which must affect spatial relationships of organelles and metabolic systems, return to normal on a time span similar to full recovery of photosynthesis. Comparison of the present data with recently published results suggests a significant role for the cytoskeleton in desiccation responses.

Fine-scale spatial and temporal changes in the population structure of terricolous bryophyte species in forest communities

The bryophyte vegetation of three acidophilous forest communities of radiolarian bedrock was investigated in the Bükk Mts in Hungary. The frequency and the spatial pattern of 7 dominant species were studied in permanent quadrate blocks for three years using Four-Term Local Quadrate Variance (4TLQV) spatial pattern analysis. The size of quadrate blocks were 3,600 cm2 consisted of 20 × 20 cell network and the used data type were the weighted shoot density of the occurring species. The maps and variograms of the occurred terricolous bryophyte species were calculated with a program package called PASSAGE (Pattern Analysis, Spatial Statistics and Geographic Exegesis). The examined bryophyte species were: Ceratodon purpureus, Dicranum scoparium, Hypnum cupressiforme, Leucobryum juniperoideum, Polytrichum formosum, P. piliferum. Using other type of temporal observation methods the results of the analysis is useful for characterising the spatial pattern and temporal dynamics of the examined populations of these bryophyte species within a habitat type.

Effects of de- and rehydration on food-conducting cells in the moss Polytrichum formosum: a cytological study.

Moss food-conducting cells (leptoids and specialized parenchyma cells) have a highly distinctive cytology characterized by a polarized cytoplasmic organization and longitudinal alignment of plastids, mitochondria, endoplasmic reticulum and vesicles along endoplasmic microtubules. Previous studies on the desiccation biology of mosses have focused almost exclusively on photosynthetic tissues; the effects of desiccation on food-conducting cells are unknown. Reported here is a cytological study of the effects of de- and rehydration on food-conducting cells in the desiccation-tolerant moss Polytrichum formosum aimed at exploring whether the remarkable subcellular organization of these cells is related to the ability of mosses to survive desiccation. Shoots of Polytrichum formosum were dehydrated under natural conditions and prepared for transmission and scanning electron microscopy using both standard and anhydrous chemical fixation protocols. Replicate samples were then fixed at intervals over a 24-h period following rehydration in either water or in a 10 microM solution of the microtubule-disrupting drug oryzalin. Desiccation causes dramatic changes; the endoplasmic microtubules disappear; the nucleus, mitochondria and plastids become rounded and the longitudinal alignment of the organelles is lost, though cytoplasmic polarity is in part retained. Prominent stacks of endoplasmic reticulum, typical of the hydrated condition, are replaced with membranous tubules arranged at right angles to the main cellular axis. The internal cytoplasm becomes filled with small vacuoles and the plasmalemma forms labyrinthine tubular extensions outlining newly deposited ingrowths of cell wall material. Whereas plasmodesmata in meristematic cells at the shoot apex and in stem parenchyma cells appear to be unaffected by dehydration, those in leptoids become plugged with electron-opaque material. Starch deposits in parenchyma cells adjoining leptoids are depleted in desiccated plants. Rehydration sees complete reestablishment over a 12- to 24-h period of the cytology seen in the control plants. Oryzalin effectively prevents leptoid recovery. The results point to a key role of the microtubular cytoskeleton in the rapid re-establishment of the elaborate cytoplasmic architecture of leptoids during rehydration. The reassembly of the endoplasmic microtubule system appears to dictate the time frame for the recovery process. The failure of leptoids to recover normal cytology in the presence of oryzalin further underlines the key role of the microtubules in the control of leptoid cytological organization.

A novel treatment system of wastewater contaminated with copper by a moss

A novel treatment system of wastewater contaminated with copper was developed by using some mosses that are demonstrably metal tolerant and accumulate heavy metals into the cells. Scopelophila cataractae could remove copper more efficiently than other mosses, i.e. Physcomitrella patens and Polytrichum formosum. One hundred milligram per liter of copper ion was removed completely for 9 d using the suspended cultivation system flowing air coupled with intermittent mechanical disruption of the protonema filaments of S. cataractae by a homogenizer.

Structural features of Polytrichumformosum Hedw. populations along a habitat sequence of cutover restoration in the eastern Tibetan Plateau

AbstractIn order to detect the effects of forest harvesting on bryophyte populations, structural parameters (frequency, coverage, density, height, and biomass) of Polytrichum formosum Hedw. populations in the eastern Tibetan Plateau were investigated on four cutover habitats which had been harvested by clear‐cut in 1998, 1997, 1994 and 1990, representing restoration histories of 4, 5, 8, and 12 years, and on nearby primary spruce forest. Vascular plant coverage including shrubs, herbs and litter was estimated as well. It was found that the moss was not recorded in the nearby primary spruce forest but occurred on all clear‐cut habitats. The frequency index, coverage, average height, shoot density and biomass on all cutovers was 23.8±10.3% (±SD), 1.8±2.5%, 105.5±53.3 mm, 1,358.9±1,744.1 shoot/m2 and 7.3±12.5 g/m2, respectively. The moss population on clear‐cut habitat was an invading pioneer moss, and the structural parameters showed large‐scale variability, agreeing with the initial hypothesis that deforestation promoted the establishment of the moss, which prefers light, on clear‐cut habitats. Of all structural parameters, only the average height increased across clear‐cut habitats along the restoration sequence. The relationships between the structural parameters and vascular coverage indicated the moss only occurred patchily on clear‐cut habitats. The population occurrence potentially depended on shrub coverage, and the development was crucially controlled by herb coverage. The results suggested that the present structure of P. formosum populations on the clear‐cut habitats was the result of environmental degradation resulting from forest clear‐cut logging, population biology and reproductive strategies.

Growth and Development of Mosses are Inhibited by the Common Herbicide Asulam

Protonemata of three mosses (Bryum rubens Mitt., Campylopus introflexus (Hedw.) Brid,. and Polytrichum formosum Hedw.) were exposed in sterile cultures to low concentrations of the bracken herbicide asulam, added to the solidified growth medium. Protonemata were either exposed for 24 hours and then transferred onto media without asulam, or exposed constantly to the asulam media. Growth was measured over a three-week period as the mean of two plug diameters, and development of leafy gametophores was noted. A 24-hour exposure period to asulam had no effect on the growth or development of the mosses at concentrations of 0.001–1 g a.i. (active ingredient) l−1. The growth and development of all three species was significantly affected by continuous exposure to asulam at concentrations of 0.01 g a.i. l−1 and above. Dose-response curves were fitted to the data and EC50 values calculated. Campylopus introflexus was the least sensitive species tested and P. formosum the most sensitive, with a 10-fold difference in sensitivity between the two. The sensitivity of B. rubens was closer to that of C. introflexus than to P. formosum. The sensitivity of mosses exposed to asulam is discussed in relation to previous laboratory experiments.

GROUND BRYOPHYTE COMPOSITION AND SYNUSIA STRUCTURE UNDER SIX TYPES OF YOUNG CONIFEROUS FOREST PLANTATIONS IN THE UPPER MINJIANG RIVER

Bryophytes on the ground under six types of artificial forests, Picea balfouriana forest (P), Pinus tabulaeformis forest (Y), Pinus armandii forest (H), Larix kaempferi forest (L), Picea balfouriana-Pinus tabulaeformis forest (P-Y) and Pinus tabulaeformis-Pinus armandii forest (Y-H), were investigated in the upper Minjiang River in order to understand the bryophyte composition and synusia structure of these different forest types. In the 19 bryophyte species identified, only 13, 10, 7, 11, 9 and 10 species were present in the P, L, H, Y-H, Y and P-H forests, respectively. Four mosses, Brachythecium glaciale, Thuidium cymbifolium, Entodon concinnus and Eurhynchium savatieri, were common in all six plantations. Another three mosses, Entodon macropodus, Mnium spinosum and Polytrichum formosum, occurred only in the Picea balfouriana forest. The highest frequency of bryophyte occurrence was under the P forest (90%) and the lowest frequency under the H forest ( 17.65% ). Thuidium cymbifolium had the highest frequency (60%) of all species under the P forest, and the second was Brachythecium glaciale (50%). The predominant species, based on the importance value, was Thuidium cymbifolium under the P forest and Brachythecium glaciale, occurred under the other five plantations, which indicated that Brachythecium glaciale was the most common moss species in the study area. In all forests, the P forest had the highest bryophyte diversity (Shannon-Wiener index, species richness index) and the H forest had the lowest diversity. The lowest Simpson index was calculated for the H forest and the highest one for the P forest. The highest similarity index (Sorensen similarity) occurred between the H and Y forests (0.89) and the lowest similarity index between the P and H forests (0.40). The greatest percent coverage (17.79%±1.67%), shoot density ((3 807.11±412.90) shoots·m -2 ) and thickness ((19.89±1.69) mm) of bryophytes occurred under the P forest, and the lowest values (0.41% ±1.49%, (27.99±367.95) shoots·m -2 , and (1.80±1.51) mm, respectively) under the H forest. For the Y, L, Y-H and P-H forests, ground bryophyte cover was 5.20%±1.58%, 2.44%±1.58%. 2.73%±1.61%, and 2.71%±1.61%, respectively, shoot density was (623.08±391.71), (566.13±391.71), (253.38±398.41), and (188.69±398.41) shoots·m -2 , respectively, and average bryophyte thickness was (9.60±1.61), (14.93±1.61), (9.59±1.63), and (6.69±1.63) mm, respectively. No statistical differences (p0.05) were found in any of these measures among the Y, L, Y-H and P-H forests. The low bryophyte diversity and limited structure development (density, coverage, thickness) found under all six plantations indicate that, in general, these are poorly developed bryophyte communities. Our results show that the best bryophyte community have developed under the spruce forest with a relatively open canopy and low tree density. Our results suggest that tree thinning or canopy pruning would be an effective measure for improving bryophyte development under dense forests.

Relationship between field-layer vegetation and canopy openings in a Carpathian subalpine spruce forest

The field-layer structure relative to the distribution of canopy gaps was analysed in a subalpine spruce forest in the Babia Gora massif – one of the highest in the Polish West Carpathians. Nineteen synusiae (floristically, physiognomically and ecologically homogenous one-layered vegetation units) in the field-layer were distinguished on the basis of the dominance of 8 vascular plants and 1 moss species. The presence of synusiae was noted in a grid of points spaced at 10 × 10 m which was established in a 14.4 ha area. This grid was then laid over a map of gap distribution. The main results are: 1. Nearly 2/3 of the area was covered with two mono-dominant synusiae: Athyrium distentifolium and Vaccinium myrtillus. 2. The spatial structure of the field layer was related to the distribution of gaps. A significant departure from a random distribution was noted for eight synusiae, which together covered 88% of the area under the spruce canopy and 92% in gaps. 3. The percentage of area covered by Athyrium distentifolium in gaps was nearly twice as great as outside them. A positive relationship to gaps also showed patches dominated by Calamagrostis villosa and Dryopteris dilatata + Rubus idaeus, while a negative relationship occurred for synusiae dominated by: Dryopteris dilatata, Vaccinium myrtillus, V. myrtillus + D. dilatata, and V. myrtillus + Polytrichum formosum. 4. There were significant differences in the structure of the field layer between the understory of closed stands and in gaps larger than 50 m2. This means that even a small-scale disturbance touching a few trees and causing only a small modification in light and soil conditions can result in considerable changes in the field-layer vegetation in subalpine spruce forests.

Coumarins give misleading absorbance with Ellman's reagent suggestive of thiol conjugates.

In the course of a screening for phytochelatins in cadmium-exposed bryophytes in the terrestrial mosses Polytrichum formosum and Atrichum undulatum we detected compounds with absorption properties and retention times similar to phytochelatins when applying the commonly used standard method RP-HPLC and post-column derivatization with thiol-specific DTNB (Ellman) reagent. Moreover, as with phytochelatins known in other plants, the concentrations of these compounds increased slightly after Cd stress. The concentration of the precursor glutathione (gamma-ECG), however, increased in the presence of Cd. In order to verify the identity of these putative phytochelatins we performed LC-ESI-MS analyses as well as 1H NMR on extracts from P. formosum and A. undulatum. Spectroscopic investigations indicated that the detected compounds were neither phytochelatins nor other thiol compounds. From the results of HPLC-1H NMR and mass spectrometry we concluded that at least one of these substances was a coumarin, probably a 5,8-dihydroxy-7-methoxycoumarin-5-beta-glucopyranoside, which has already been described for A. undulatum and P. formosum. The results of our investigations prove that under the basic pH conditions essential for the Ellman test for thiol compounds, coumarins show comparable UV/VIS absorption properties. Therefore, a positive post-column Ellman reaction cannot unambiguously prove the presence of thiol-containing compounds in plants.

The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites.

Using highly polymorphic microsatellite markers, we assessed clonal structure and paternity in a population of the bryophyte species Polytrichum formosum. Identical multilocus genotypes of individual shoots were almost never observed in spatially separated cushions, but were found to be highly clustered within moss cushions. Therefore, asexual reproduction through dispersal of gametophyte fragments is not very important in P. formosum. However, asexual reproduction on a very localized scale through vegetative growth of genets (branching of gametophytes via clonal growth of rhizomes) is very extensive. The patchy spatial distribution of genets and the absence of intermingling among genets suggest that this species follows a 'phalanx' clonal growth strategy. Vegetative proliferation of genets will increase their size, and, consequently, will have considerable fitness consequences for individuals in terms of increased genet longevity and reproductive output. Although paternity analysis of sporophytes confirmed male genet size, i.e. gamete production, to be an important determinant of male reproductive fitness, it also showed that the spatial distance to female genets is the predominant factor that governs male reproductive success. Moreover, we showed that male gamete dispersal distances in P. formosum are much further than generally assumed, and are in the order of metres rather than centimetres. Combining the findings, we conclude that the high genotypic diversity observed for this facultatively clonal species is most likely explained by a preponderance of sexual reproduction over clonal reproduction.

Genetic Evidence for the Allodiploid Origin of the Moss Species Polytrichum longisetum

Abstract: Fixed heterozygous banding patterns observed for 4 allozyme and 12 microsatellite loci, in combination with a chromosome number of 14, show that Polytrichum longisetum is an allodiploid species. Comparison of these banding patterns with those of related Polytrichaceae species suggest that Polytrichum formosum, or an ancestor taxon of this species, is one of the haploid progenitors of P. longisetum. The second progenitor species of P. longisetum could not be designated in this study as it was not among the examined possible progenitor species. DNA sequence data for two microsatellite loci, however, suggest that the second progenitor species should possibly be more closely related to P. formosum than any of the other haploid possible progenitor species examined in this study. As the current systematic literature does not mention the existence of such a species, this could indicate that the second progenitor species is already extinct.

Growth morphology and genetic diversity of Polytrichum populations

This study is a comparative analysis of architectural structure and internal genetic variability of populations of two common moss taxa: Polytrichum formosum and Polytrichum commune var. perigoniale. The genetic diversity within populations of the two taxa was evaluated by RAPD analysis using 11 different primers. Among five populations analyzed for each taxon, nine genotypes of P. formosum and 13 genotypes of P. c. var. perigoniale were detected. Each population was constituted of several genotypes (averages of 4 and 4.6 for P. formosum and P. c. var. perigoniale, respectively). The diameter of radially arranged leaves appeared to play an important role in the regulation of growth in Polytrichum populations. For both taxa, results showed a specific and sexual dimorphism for size in this feature. The present study did not allow any assessment of the correspondence between the architecture and genetic structure of populations. Stem-density profiles for different stem cohorts among populations showed a predominant cohort, with a single central distribution of a first year cohort for both taxa. Populations extended their surfaces by the overlaying of successive stem cohorts. In terms of stem-density profile, the genotypes were structurally indistinguishable within the population.

Genetic structure of Polytrichum formosum in relation to the breeding system as revealed by microsatellites

Abstract Microsatellite variation was determined for three Danish and three Dutch populations of the haploid moss species Polytrichum formosum to gain insight into the relative importance of sexual vs. asexual reproduction for the amount and structure of genetic variation. In general, low levels of microsatellite variation were observed within this species. Even when estimated for polymorphic loci only, the levels of microsatellite variability (P=90.6, A=4.3 and HS=0.468) within populations were on average lower than those reported for most other plant species. In contrast, genotypic diversity was high within each of the examined populations, indicating that sexual reproduction is a very important determinant of the genetic structure of P. formosum within populations. In agreement with previous findings for allozyme data, no significant genetic differentiation (FST=0.028, RST=0.015) was observed neither between populations nor between regions approximately 450 km apart (Denmark vs. the Netherlands). These low levels of population differentiation observed for both types of genetic markers are probably best explained by a high level of effective spore dispersal (gene flow) between populations. Therefore, also on a large geographical scale sexual reproduction is the most important determinant of the genetic structure of P. formosum, despite the high potential to reproduce clonally.

How to Crawl and Dehydrate on Moss

Tardigrades ( Macrobiotus sp., Echiniscus testudo) were videotaped when moving on single plants of mosses with different water retaining capacities. On a fully hydrated Encalyptra contorta plant encased in a continuous water column, tardigrades could hardly crawl rapidly in a specific direction. This was probably due to their low specific weight and the poor ability of their claws to cling to the substrate. As tardigrades were not able to walk on the undersurface of the leaves under these conditions, they were rinsed out of a fully soaked moss cushion in the course of time. Fully hydrated Polytrichum formosum plants did not show a visible water film and locomotion of tardigrades could not be observed on this moss. Activity of animals appeared to be confined to the droplets in the leaf axils. During dehydration, the tardigrades stopped moving and formed a tun on the spot.

Amount and structure of intra- and interspecific genetic variation in the moss genus Polytrichum.

Allozyme electrophoresis was used to determine amount and structure of genetic variation within and between five congeneric haploid moss species: Polytrichum formosum, P. commune, P. uliginosum, P. piliferum and P. juniperinum. For the different species, gene diversity within populations (HS) ranged from very low (0.025) to moderate values (0.127), being, on average, lower than those observed for vascular plants and many other moss species. Polytrichum piliferum and P. juniperinum showed significantly higher levels of HS than the other species examined, which possibly might be explained by sexual reproduction being more prevalent in these two species, that often live in more dynamic habitats, where turnover of individuals is more frequent. Genetic variability was observed to be structured in contrasting ways at different levels. At the intraspecific level genetic differentiation among populations of most Polytrichum species was low, FST </= 0.1, indicating a considerable degree of gene flow by wind-dispersed spores over substantial distances. At the interspecific level strong divergence, genetic identities being on average I=0.222, was observed between most species studied, despite low levels of divergence at the morphological level. These I-values are significantly lower than observed for congeneric vascular plant species and most congeneric bryophyte species. This suggests that the morphological conservatism is not due to lack of genetic variability and evolutionary potential.

Deposition and disease: a moss monitoring project as an approach to ascertaining potential connections

In the years 1995 and 1996 the atmospheric deposition of elements in the EuroRegion Neisse (ERN) was determined in a biomonitoring project using mosses. The mosses Pleurozium schreberi and Polytrichum formosum were chosen as biomonitors because of their wide distribution in the area studied. The moss samples were analysed by ICP-MS and ICP-OES for their concentrations of 37 chemical elements. The results were shown in the form of maps. The data from the moss monitoring project served as a basis for determining those elements in the deposited material that promote the occurrence of disease. This was done by correlating the figures for the various diseases with the appropriate element concentrations in the mosses. Indications were found that a connection exists between the thallium content of mosses and the occurrence of cardiovascular disease and between Ce, Fe, Ga and Ge levels in the mosses and the incidence of diseases of the respiratory system.

A note on the stable carbon isotope composition of bryophytes in calcareous aquatic habits and its relationship to carbon dioxide assimilation

The stable carbon isotope composition of six bryophytes (five from a hardwater spring, one from heathland) varied with the carbon dioxide source. Palustriella commutata growing in calcareous springwater was most depleted in 13C and Polytrichum formosum, the heathland species was the least depleted. The pattern of depletion was consistent with the observed availability of 13C-depleted groundwater. The springwater bryophytes were also associated with travertine deposition and demonstrated the probable existence of a photosynthetically-driven travertine component.

Lead Isotope Systematics in Polytrichum formosum: An Example from a Biomonitoring Field Study with Mosses

With the aid of inductively coupled plasma mass spectrometry (ICP-MS), {sup 206/207}Pb isotope ratios were determined in 34 moss samples (Polytrichum formosum) taken from the Hoerner Bruch area near Osnabrueck (FRG) in the years 1987--1996. The goal was to distinguish different sources of atmospheric lead pollution by the investigation of lead isotope ratios. Reproducibility tests were carried out to ensure the reliability of analyzing Pb isotope ratios in moss samples by means of quadrupole ICP-MS. The reproducibility of the isotope ratios for one digested sample and the day-to-day reproducibility were determined. In all the moss samples analyzed, relative standard deviations of < 0.26% for five replicate measurements of one digested sample were achieved for the {sup 206/207}Pb isotope ratios. On the basis of the {sup 206/207}Pb isotope ratio, it was possible to establish that the sources of man-made atmospheric inputs of lead have changed over the 10-year period investigated. In the moss samples analyzed, the {sup 206/207}Pb isotope ratio was found to have risen significantly from 1.131 in 1987 to 1.154 in 1996. This increase in the {sup 206/207}Pb isotope ratio can be attributed to a reduction of atmospheric inputs of lead from petrol.